Medical catheters are adapted for insertion into a body cavity, duct, tract, organ or blood vessel in order to facilitate any of a wide variety of diagnostic or therapeutic functions. Such catheters generally include an elongated, flexible catheter tube or body whose side wall encloses at least one catheter lumen extending from a proximal catheter body end, which is coupled to a catheter hub, to a distal catheter body end. The catheter body may be relatively straight or inherently curved or curved by insertion of a curved stiffening wire or guide wire or curved by built-in control wire-deflection. The catheter sidewall is typically fabricated and dimensioned to minimize a catheter body outer diameter and sidewall thickness and to maximize the catheter lumen diameter while retaining sufficient sidewall flexibility and strength characteristics to enable the catheter to be used for the intended medical purpose. Examples of medical catheters include but are not limited to electrophysiology catheters, guiding catheters, drainage catheters, perfusion catheters and drug infusion catheters.
Desirable qualities of catheters include a stiffness facilitating torque transfer and pushability balanced with a flexibility facilitating tracking through tortuous anatomy, lumen lubricity to facilitate passage of other catheters or devices or substances therethrough, and a sidewall strength that prevents kinking. Additionally, it is desirable to provide a smooth and relatively soft catheter distal tip, to prevent damage to surrounding tissue as catheter is advanced, and a radiopaque marker near the distal tip to enhance catheter visibility under fluoroscopy. To achieve the aforementioned qualities it may be necessary to form a catheter body from a plurality of segments.
A typical technique employed to join catheter body segments involves assembling a mandrel through the lumens of catheter body segments and then fusing the segments together by means of heat applied while the segments are held within a tube, for example a PTFE tube. Frequently, the joint that is achieved is enlarged or is flawed in other respects. If one of the catheter segments includes reinforcement in the form of braided or coiled wire filaments or strands within a sidewall, the strands, in proximity to the fused joint, may unravel or shift such that they protrude out through the outer surface of the fused joint. This can occur due to a high tensile strength of the wire filaments and the winding tension that is applied during formation of a tight wire braid or coil. There remains a need for a fabrication technique that simplifies fabrication steps and reduces scrap and other costs while retaining desirable characteristics of the catheter body.